In the field of electronic testing and diagnosis of defects in circuit boards, it is necessary to effect electronic probe contact with components on the circuit board under test. One type of known testing technique makes use of the edge connections of the board as probing contacts for the various components thereof. Such a technique requires diagnostic iteration through a series of time consuming excitation and response tests to identify the location of faults in the circuit board under test.
Another type of known testing technique, specifically directed to avoid the foregoing iterative testing processes, uses the so-called "bed of nails" test fixture wherein an array of contact pins mounted through a perforated platform is arranged to contact the plated side of the circuit board. As shown, for example, in the German Offenlegungsschrift No. 2051052, an array of double-ended spring-loaded pins is positioned between the plated side of a board under test and a plurality of electrically conducting leads coupling the pins to an electronic test equipment.
As the operating speed of logic components increases, electronic testers must have the capability of testing circuit boards at higher frequencies. The proper design of a test fixture which provides the interface between an electronic tester and a circuit board becomes critical to achieve reliable test results. Traditional test fixtures using straight or twisted pair wires connecting a bed of nails to the electronic test equipment may generate crosstalk, ground noise and ringing effects. These deleterious effects are most prevalent at high frequencies. Furthermore, the effective lead inductance associated with the wiring can become problematic during in-circuit testing. Using double-ended spring-loaded backdriving and ground pins in combination with a stripline board does not, of itself, reduce the inductance of the circuit formed by the pins and the boards. Therefore, there exists a need for a high frequency fixture which reduces noise and decreases the effective lead inductance of the transmission medium used.